The present invention relates to a composite machining lathe having a tool magazine storing a plurality of different tools and adapted to successively conduct various machinings by selectively changing and using these tools.
To comply with the current demand for diversification of machining of machine parts or the like, lathes known as composite machining lathes, capable of performing various machining tasks through selective use of a plurality of tools, have been developed and put into practical use.
In these lathes, the various types of machining are successively conducted through sequential exchange of a variety of tools. To handle diversified machining tasks, therefore, it is necessary to prepare a large number of tools in a ready-to-use fashion.
Generally, the composite lathes of the type described can be categorized into turret-type lathes having a turret carrying a multiplicity of tools and adapted to be indexed to bring one of the tools to the machining position, and ATC arm-type lathe having an automatic tool exchanger equipped with an ATC (Automatic Tool Changing) arm adapted to deliver tools from a tool holder base to a tool magazine separate from the tool holder base and vice versa thus conducting a tool exchange.
The turret-type composite lathes suffer from a disadvantage in that the number of the tools which can be held by the turret is limited undesirably. Namely, if the number of the tools is increased unlimitedly, an interference tends to occur between adjacent tools or between the tools and the work. For mounting as many tools as possible on a turret having a given size, much time and skill will be required for attaining such a tool layout as to avoid the interference mentioned above.
On the other hand, the ATC arm-type composite lathes requires a considerably long time for the transfer of tools between the tool magazine and the tool holder base for the tool exchange by the ATC arm, although the problem of interference and the limitation of number of the tools is not so severe in this type of lathe as in the turet-type. In addition, the arrangement around the tool holder base is complicated and becomes large in size because it is necessary to provide a mechanism for driving the ATC arm. Furthermore, a large driving power is required for driving the tool holder base and other movable parts. In consequence, the lathe as a whole becomes complicated and large in size.
Moreover, both types of composite machining lathe involve a common disadvantage in that, when a tool which is hot carried by the turret or the tool magazine is to be used, the operator has to manually set the new tool on the turret or the tool magazine. This manual work is quite troublesome and time-consuming. Thus, the operator is heavily burdened and preparation time is impractically prolonged for the setting of tools particularly in the case of a large-lot and small-quantity production which is often demanded in the current style of production.
It would be possible to obviate these problems by using a turret or magazine of increased size so as to permit the mounting of as many tools as possible. Such turret or tool magazine having an increased size, however, inconveniently prolongs the time required for the tool indexing or exchange, i.e., for the tool selection, resulting in a prolongation of loss time.